Ignition Duration Research Articles

Integrating micro-ignitors with Al/Bi2O3/graphene oxide composite energetic films to realize tunable ignition performance

The integration of composite energetic films (CEFs) with various types of initiators can effectively adjust their performance and represents potential applications in microscale energy-demanding systems. In this study, the Al/Bi2O3/graphene oxide (GO) CEFs were successfully integrated into copper micro-ignitors by electrophoretic deposition, a low-cost and time-saving method. The effects of the Al/Bi2O3/GO CEFs with different GO contents on exothermic performance and ignition properties of micro-ignitors were then systematically investigated in terms of heat release, activation energy, ignition duration, the maximum height of the ignition product, and ignition delay time. The results showed that the addition of GO promoted more heat releases and higher activation energies of Al/Bi2O3/GO CEFs. The addition of ≤3.5 wt. % GO prolonged the ignition duration from 450 μs to 950 μs and increased the maximum height of the ignition product from about 40 mm to 60 mm. However, the micro-ignitors with more than 3.5 wt. % GO cannot be ignited, which suggested that GO played a contradictory role in the ignition properties of micro-ignitors and the controlled GO content was a prerequisite for improved ignition performance. The ignition delay time gradually extended from 10.7 μs to 27.6 μs with increases in the GO contents of Al/Bi2O3 CEFs, revealing that an increase in the weight ratio of GO leads to lower ignition sensitivity of micro-ignitors.

Studies of Carbonization Process on the Production of Durian Peel Biobriquettes with Mixed Biomass Coconut and Palm Shells

Biobriquettes as alternative energy that can replace the role of kerosene. Biobriquettes made from agricultural waste biomass. Biobriquettes durian peel has been researched and developed continuously to obtain optimal quality in terms of calorific value, compressive strength and duration of ignition. In making durian peel biobriquettes needed other biomass mix to sustain duration of Ignition for biobriquettes durian skin quickly burned out. Stages of making biobriquettes durian skin are: material of drying, carbonization of biomass, grinding, mixing with adhesives, and printing. Carbonization process is a process that is important in obtaining the biomass charcoal. Carbonization is done by means of karbonisator pyrolysis. The purpose of this research is to study the process of carbonization to obtain biobriquettes durian skin that of quality in terms of value compressive strength, calorific value, and duration of ignition. Variations that done was kind mix of biomass,coconut shells and palm shells with the massa ratio 2 : 1, type of adhesive used tapioca powder and banana peels, carbonization of temperature 200°C. 300°C and 400 °C. The results showed that the highest compressive strength of the durian skin with a mixture of coconut shell and adhesive tapioca powder and carbonization temperature of 300 °C namely 12,7 g/cm2. The calorific value of the highest on the mix of skin durian with coconut shells and adhesive banana skin with temperature of carbonization 400 °C ie 6040 cal/g, and duration of ignition highest on a mixture of skin durian with coconut shell and adhesive banana skin at a temperature of carbonization 300 °C is 73 minutes.

Approximate model of wet particle drying

When plant refuse burning process of drying of fuel is transferred to the furnace camera. Drying of large particles of fuel from the very beginning proceeds in the period of the drooping combustion rate. At the same time the front of evaporation goes deep in material, volatile components and coke residual are separated and firing. In the conditions of convective and radiant heat exchange with the combustion gases which are in case of high temperature, the particle practically at once gets warm to a water boiling temperature. At the same time process of intensive evaporation of moisture which front moves deep into material begins. «Dry» and «wet» zones are formed in a particle. Warming up, separation of volatile components and their inflaming in «dry» zone begin in the course of a deepening of evaporation zone. Three periods of drying are provided for burning of a large particle of the wet fuel with a radius more than 1 mm: before inflaming of volatile components; visible burning of volatile components before inflaming of coke on a surface; the drying proceeding in parallel with coke burning-off. A certain location of an evaporation zone corresponds to each of these periods. And we can calculate particle dryness and drying duration. Summary time of drying represents duration of particle ignition. Processes of particles drying and ignition with different initial humidity and under various conditions of a heat emission were calculated. Drying, separation and inflaming of volatile components, as well as burning of coke residual take place at the same time in a large wet particle of plant refuse in case of arrival into the furnace camera. Duration of ignition is defined by end time of burning of coke residual and can be calculated according to complete drying of a particle. In the furnace unit TBR-2.0 drying and ignition of the wet soft plant refuse particles with a radius less than 0.25 mm takes less than for 2 s, drying with the subsequent ignition of particles with a radius of 1-3 mm continues 30 s.

Drying grain using solid fuel

The use of alternative sources of liquid (gaseous) fuel to produce a coolant, including for grain drying, has been studied in contrast to burning conventional fuels, which hinders their use. A characteristic feature of the use of combustion units for burning plant waste is a sufficiently long ignition and preheating, preceding the drying. At the same time, a large amount of heat is accumulated in the furnace casing, which can be partially used for batch drying for the next batch of grain and completely for the latter, which will increase the efficiency of the process. Drying is one of the main operations in post-harvest grain processing, the fate of the crop depends largely on the quality of drying. Both flow and periodic drying are common in farms. Periodic drying, as a rule, uses the same dryers as for flow or specialized. The technology of this drying in dryers equipped with liquid or gas furnaces is well developed and does not cause difficulties - kindle the furnace, cyclically dry the grain to the conditioned moisture, cut off the fuel supply, cyclically cool and unload the dryer. The pause between the drying of adjacent lots without ignition and heating of the furnace is determined by the cooling time of the masonry to the temperature of stable ignition and burning of volatiles plus 150-200 °С, depending on the moisture content of solid particles of plant waste. The duration of ignition is a function of the mass of the furnace chamber, its heat capacity, the temperature of the flue gases and the heat transfer coefficient. At ignition of liquid fuel its duration is not less than 20 min. To dry the last batch of grain, the mass of the burnt chamber must be at least 0.7 times the mass of the grain in the dryer. The duration of heating the furnace is completed by stabilizing the temperature of the flue gases at the outlet of the exhaust fan, but not less than 1 hour.

Characteristic of energetic semiconductor bridge based on Al/MoOx energetic multilayer nanofilms with different modulation periods

Three types of energetic semiconductor bridges (ESCBs) through integrating different Al/MoOx energetic multilayer nanofilms on a semiconductor bridge have been investigated in this study. The relationships among the critical firing energy, critical firing time, total firing time, and ignition energy as well as the input energy utilization efficiency of these initiators were analyzed. The principal component analysis (PCA) was utilized in the experiments to evaluate the output energy magnitude based on the ignition duration, the maximum flame area, reaction ratio, and other parameters. The results obtained were as follows: (1) The critical firing energy is positively proportional to the modulation periods of nanofilms for the initiators discharged with identical voltage, while the total firing energy and the input energy utilization efficiency do not change significantly; (2) by using PCA, the composite score of the ESCB/50 nm, ESCB/150 nm, ESCB/1500 nm, and SCB is measured at 3.025, 0.250, −1.433, and −1.842, respectively, discharge with 30 V/47 μF, which indicated that the output energy of ESCBs can be increased significantly by decreasing the modulation periods of nanofilms.

Ignition characteristics of solid cone fuel spray of a high speed diesel engine

An experimental study of the ignition characteristic of solid cone fuel spray for a high speed diesel engine for diesel fuel at various injection pressure (100 bar, 200 bar and 300 bar) is carried out to get the effect of injection pressure on ignition delay and duration of burning. The ignition delay of diesel fuel spray was measured by recording the time delay between the event of ignition and the event of appearance of flame inside the combustion chamber by using digital storage oscilloscope. For this purpose an experimental set up was developed with the emphasis on optical method for detecting flame. The measurement of ignition delay was taken at various cylinder pressures (20, 30 and 40 bar) for different surface temperature (623K, 673K and 723K). Main objective of this project was to study the parameter of emission and their control. The result presented here shows that, ignition delay and duration of burning of diesel fuel decreases with increase with injection pressure and also with increases in hot surfaces temperature and also with increases in cylinder pressure.

Initiation of arcing on tungsten surface exposed to steady state He plasmas

Arcing was initiated in steady state helium plasmas by negatively biasing a tungsten electrode to around −500 V. On the tungsten electrode, nanostructures were grown by the plasma irradiation. In this study, we characterized the property of the initiated arcing by measuring the temporal evolutions of the electrode potential and the arc current. The ignition frequency and duration of arcing were presented from the potential measurements; the arc duration was in the range of <10 ms and the distribution altered when changing the biasing voltage. The behavior of arc spots was observed with a fast framing camera. It was shown that the spots split frequently, and sometimes, they run on the surface independently. From the fluctuation of the arc current, the fractal feature of arcing was revealed.

A Study of Cotton Dust Mixed with Wood Dust for Bio-Briquette Fuel

Various textile-industrial wastes such as cotton wastes, polyester fibres, lumps and old rags can be a source of energy. Cotton dust seems to be one of the most interesting bio-waste energy sources because its shares of the high heat energy and organic material. This paper presents physical and mechanical properties of briquette mixed with cotton dust (CD) and wood dust (WD). The various ratios of CD:WD (0:100, 20:80, 40:60, 60:40, 80:20 and 100:0 % by weight) were investigated. The dimensional of hexagon briquette specimen was 5 cm (outer diameter) and 2.5 cm (hollow inner diameter) with the height of 10 cm was subjected to physical and mechanical tests. Results of physical performance test showed that the briquette specimens with ratio of CD:WD (1:0) gave the lowest ignition temperature, smoke temperature and duration of flame out time of 280°C, 275°C and 6.30 min/2gm respectively. While, the briquette specimens made with ratio of 0.2:0.8 gave the highest heat energy of 3,960 cal/g. However, the result of mechanical properties showed that and briquette specimens made with the ratio of 0.2:0.8 was the highest compressive strength of 9.80 N/mm2. This study indicated that CD can be used as a substitute material for bio-briquette fuels.

Extraction of petrol products from water by magnetite-based sorbents

The results of studying the effectiveness of petroleum extraction from water by their sorption on magnetite particles are given. It was found that magnetite particles, obtained by chemical condensation have the high dispersion ability, which prevents their practical use in industrial processes. It is possible to significantly change the particle size distribution of the magnetite mixture by treating them with petroleum products followed by ignition at high temperatures. The main factors, affecting particle size distribution of the mixture after such treatment is dose of petroleum products, the temperature and duration of mixture ignition. It was determined that the optimum ignition temperature is 300°С, at which the largest number of aggregates with sizes of 30 - 40 microns is produced. Particle size distribution is significantly affected by the ignition duration that we associate with the residual content of petroleum products that do not manage to decompose under short ignition duration and act as a binder for magnetite particles. At low doses (ratio of petroleum products: magnetite within 0.083 - 0.025), there was no significant effect on the particle size distribution of the treated mixture. In certain circumstances, the number of sorption: ignition cycles does not affect the particle size distribution of the mixture, allowing to form filtering media with stable hydraulic and sorption properties.

Estimating soil organic carbon through loss on ignition: effects of ignition conditions and structural water loss

SummaryLoss on ignition (LOI) is one of the most widely used methods for measuring organic matter content in soils but does not have a universal standard protocol. A large number of factors may influence its accuracy, such as furnace type, sample mass, duration and temperature of ignition and clay content of samples. We conducted a series of experiments to quantify these effects, which enabled us to derive (i) guidelines for ignition conditions (sample mass, duration and temperature), (ii) temperature‐specific soil organic matter (SOM) to soil organic carbon (SOC) conversion factors and (iii) clay content‐dependent correction factors for structural water loss (SWL). Bulk samples of a sandy soil (4% clay) and a silt loam soil (25% clay) were used to evaluate the effects of ignition conditions. Samples with a range of clay contents (0–50%) were used to quantify conversion and correction factors. Two furnaces, one without and one with pre‐heated air, did not show significant differences in terms of within‐batch LOI variability. In both furnaces less combustion occurred close to the door, which necessitated tray turning at half‐time as this reduced the standard deviation per batch significantly. Variation in mass loss declined exponentially with sample mass (range, 0.15–20 g). The LOI increased with duration at lower temperatures (≤ 550°C) for the sandy soil. At greater temperatures (600 and 650°C), no effect of duration was found. For the silt loam soil, LOI values increased with duration for each temperature, which was attributed to SWL. The SOM to SOC conversion factor decreased strongly with temperature at an ignition duration of 3 hours from 0.70 (350°C) to 0.57 (500°C) and stabilized around 0.55 between 550 and 650°C, indicating that at temperatures ≥ 550°C all SOM had been removed. The clay correction factor for SWL increased from 0.01 to 0.09 as the temperature of ignition increased from 350 to 650°C. To minimize within‐batch LOI variation we recommend a standard ignition duration of 3 hours, tray turning at half‐time, a sample mass ≥ 20 g and temperatures equal to or greater than 550 °C. To avoid over‐estimates of SOM through structural water loss, the presented SWL correction procedure should always be applied.

Характеристики зажигания частиц угля и капель суспензионного топлива при кондуктивном нагреве

This article presents the experimental investigation results of ignition of particles and dust of lignite coal (B2 rank, Krasnoyarsk region, Borodino deposit) as well as slurry fuel droplets (mixture of coal dust and water) based on this coal at interaction with heated surface. The studies are focused on determining the mechanisms and conditions of ignition of organic fuels (which are used in thermal power plants) at direct contact with heated surface. Conductive heat transfer is typical for actual conditions of technological processes at interaction of fuel particles or droplets with heated surfaces of power equipment at the stages of preparing components, their filtration, drying, transportation and supply to combustion chambers. For several characteristic sizes (from 1 to 5 mm) of the coal particles we determined the duration of inert heating until the implementation moment of intense exothermic process in the range of heat source temperatures from 600 to 850 °С. Similar results were obtained for slurry fuel droplet with characteristic size of 5 mm. The significant influence of coal particle sizes on their ignition delay times was revealed. Analysis of experimental results showed, that the process duration of ignition initiating for slurry fuel droplet considerably exceeds (more than 20 %) the similar characteristic for coal particle under the identical research conditions.

The effects of thermal and compositional stratification on the ignition and duration of homogeneous charge compression ignition combustion

In this work, the effects of thermal and compositional stratification on the ignition and burn duration of homogeneous charge compression ignition (HCCI) combustion are studied with full-cycle 3D computational fluid dynamics (CFD) simulations with gasoline chemical kinetics performed during the closed portion of the cycle, from intake valve closing (IVC). The stratification was varied through the use of negative valve overlap (NVO) and positive valve overlap (PVO) breathing strategies. To remove charge energy and phasing effects from the simulation results, the fuel mass and ignition timing were held constant, while mean composition effects were isolated from those of local stratification by maintaining the same mean oxygen concentration, fuel–oxygen equivalence ratio and charge heat capacity. Fuel was premixed with the intake to avoid potential stratification effects arising from direct injection. With NVO, the incomplete mixing of the fresh charge with the large mass fraction of product gases retained within the cylinder from the previous combustion cycle leads to a 23% increase in the pre-ignition thermal stratification, and an order of magnitude increase in the levels of stratifications in fuel to oxygen equivalence ratio and oxygen mole fraction relative to the PVO strategy, which employs a premixed mixture of fresh and product gases. Under the conditions studied, the use of NVO resulted in a 30% increase in the 10–90% burn duration (CA10-90) compared to the PVO condition. Two additional analyses were performed to decouple the effects of thermal and compositional stratification. The first examined the reaction space (based on the ignition delay distribution within the charge prior to ignition) for both breathing strategies to quantify the inherent reactivity stratification. The second examined the more stratified NVO case with a quasi-dimensional multi-zone model. These analyses revealed that under the conditions studied, HCCI reactivity and combustion duration are governed primarily by thermal stratification and are largely insensitive to compositional stratification at the time of ignition.

Combustion, performance and emission characteristics of direct injection diesel engine fueled by Jatropha hydrogen peroxide emulsion

Recently, Jatropha, a fast growing tropical plant, has caught the attention of researchers because the oil produced from Jatropha is a non-edible. However, worse emissions, when using raw Jatropha oil in diesel engines, have been reported in the literature due to its higher viscosity and lower volatility. Therefore, it is necessary to find some way to reduce the emissions of diesel engines.In the present research, experiments have been designed and performed to study the effects of Jatropha hydrogen peroxide emulsion on combustion, performance, and the emission characteristics of a diesel engine. Hydrogen peroxide in a solution of water at a concentration of 30% was used for making the emulsions with mixing mass ratios of 5%, 10%, and 15%. A single cylinder, four-stroke, high speed, direct injection diesel engine was used for the experiments. The acquired data were analyzed for various combustion parameters such as in-cylinder pressure, ignition delay, ignition duration, heat release, for performance parameters and emissions of CO, CO2 (carbon dioxide), HC, NOx, and PM as well. While running the engine on the Jatropha hydrogen peroxide emulsion fuel, improvements in performance and emissions were found and the optimum mixing ratio of the solution with hydrogen peroxide was 15%.

Experimental Investigation of Homogeneous Charge Compression Ignition Engine of Ethanol and Diesel Blends

This paper deals with the experimental investigation of a Homogeneous Charge Compression Ignition (HCCI) Engine system. The main objective of this research work is to study the effects of a premixed fuel ratio on the performance, combustion characteristics and reduction of oxides of nitrogen and smoke intensity, using the HCCI concept. The engine used for the experiments was of a Kirloskar TAF-I series. The engine is a four stroke, single cylinder air cooled diesel engine, of a rated power of 4.4 kW loaded with an electrical dynamometer. An electronic fuel injection circuit was developed to control the ignition timing and duration of the premixed charge. Ethanol was premixed, and a part injected before ignition, whereas the diesel fuel was injected by the conventional injector directly into the cylinder. The part injected ethanol and direct injected diesel were tested in various proportions, to optimize the operating range, and the same setup was tested with various % of EGR.The obtained results include data plots illustrating the performance, combustion and emission characteristics. The results indicate that the concentration of the oxides of nitrogen species rapidly decreased, and the smoke emissions were reduced simultaneously at 20% Rp and 20% EGR in 75% load and full load conditions.

Operating Characteristics of Gasifier Cookstove Using Different Biomass Materials

Biomass energy technology such as gasifier is increasingly receiving attention as a promising renewable energy source because of the ever rising costs of fossils fuels especially diesel and kerosene. Gaseous products of gasifier based cookstove are relatively clean and environmental friendly than direct combustion cookstove. The objective of this workwas to characterize the basic operating properties of a gasifier-based biomass cookstove using different types of biomass fuels. The main characteristics evaluated were the efficiencyof the stove. The biomass considered were oil palm fronds, dry leaves and pressed sugarcane. The efficiency of the stove was tested using water boiling tests.Other characteristics such as its ignition duration and the time required to boil 2.5 kg of water were also observed. The performance of each fuel was studied by analyzing the parameters involved during water boiling tests. It was found that oil palm frond has the highest thermal efficiency among all the fuels tested.

Effect of Upgraded Lignite Product Water Content on the Propensity for Spontaneous Ignition

The spontaneous ignition that occurs with upgraded lignite products is a concern for its storage, handling, and transportation. The Basket testing method and Oxidation Kinetics testing method were used to identify the propensity for upgraded lignite products to spontaneously ignite. The evaluation index for the Basket testing method was spontaneous ignition temperatures and duration. The fundamental evaluation index (I) for the Oxidation Kinetics testing method was used to evaluate the propensity for spontaneous ignition. For both testing methods, all three of the lignite samples (Huolinhe lignite, Hailaer lignite, and Indonesia lignite) showed that the propensity for spontaneous ignition decreased linearly with the increase in water content of the upgraded lignite product. Commonly used Chinese bituminous coals, which are not prone to spontaneous ignition, were used as a benchmark for determining the recommended water content for upgraded lignite products. For Huolinhe lignite, Hailaer lignite, and Indonesia lignite, the recommended water contents of the upgraded products are 6.53%, 4.28%, and 7.83%, respectively. The method that was developed to determine the recommended water content could be used to guide engineering design and operations when using upgraded lignite that is highly susceptible to spontaneous ignition.

Characteristic Parameters Research on the Secondary Thermal Ignition of Gasoline-Air Mixture in Cave Depots

The purpose of this paper is to explore difference between the first thermal ignition and the secondary thermal ignition, and to reveal the variation rules of characteristic parameters and critical condition ignition for the secondary thermal ignition of gasoline-air mixture. In this paper, experimental investigation on the gasoline-air mixture secondary ignition induced by hot wall in model underground oil depots tunnel has been carried out. Compared to the first thermal ignition, the ignition intensity of the secondary thermal ignition is greater, while the ignition delay and duration are shorter. After the first thermal ignition extinguish, if the ambient temperature is in the range of 286K to 463K and hot wall’ temperature is in the range of 730 to 783K, then the relation between critical ignition temperature and the ambient temperature can be expressed by cubic polynomial. The critical ignition concentration of gasoline vapor is only 0.45% and that of oxygen is 10.4%.

On the Relationship Between Fuel Injection Pressure and Two-Stage Ignition Behavior of Low Temperature Diesel Combustion

In previous work, it is reported that increased dilution at midrange injection pressures produces longer first stage combustion duration. There is also corresponding decreases in nitric oxide concentrations and smoke number with respect to a reference conventional combustion mode. Continuing this effort, the objective of this study is to investigate the effect of injection pressure on the first stage ignition duration under low temperature combustion (LTC) conditions. A sweep of injection pressure is performed and the resulting heat (energy) release profiles are examined. The ignition delay behavior is expected based on changing injection pressure, but the first stage ignition duration does not follow expected trends based on initial literature review. It is postulated that the influence of injection pressure on the local equivalence ratios is causing the observed behavior. The appropriate measurement and analysis tools are not available to the authors to confirm this postulation. A literature review of work investigating ignition conditions in low temperature combustion modes is used to support the postulation made in this study.

Effect of distance, meteorology, and burn attributes on ground-level particulate matter emissions from prescribed fires

Multiple air monitoring campaigns were conducted from 2003 to 2007 during the months of December through April in which time-integrated monitoring of PM2.5 was performed during 55 prescribed burn (PB) events administered under select meteorological conditions. The data were analyzed using a generalized additive mixed-model (GAMM) where the logarithm of PM2.5 concentrations were modeled as the sum of linear and non-linear functions of our covariates of interest after accounting for the confounding associated with the grouping structure of our data and spatial dependency. Our model explained 61% of the variance of log transformed PM2.5. The GAM component of the model (i.e. our covariates of interest) explained 40% of that variance and the mixed-model component (i.e. random-effects and spatial correlation) explained 21%. Within burn events, concentrations across our air monitoring grid were significantly influenced by the distance from burn perimeter to air monitor and the proportion of time the air monitor was in line with the wind field over the burn. Among burns, variation was significantly influenced by burn duration, burn size, mode of ignition, and regional background PM2.5; indicating the importance of these for fire management. Measures of burn intensity and meteorology were found to be insignificant in our model; however, it is possible that some of these effects were absorbed by the random-effects of our model. These findings demonstrate that downwind exposure is largely a function of wind direction combined with distance from the burn and that emissions from one burn to the next are dependent on burn size, duration, and mode of ignition.

Laboratory characterization of firebrands involved in spot fires

Wildfires are considered the most important disturbance in the Mediterranean Basin, and some are propagated over long distances due to lift-off and ignition of firebrands. To improve our knowledge of firebrands involved in spotting fires, flammability characteristics of eight types of firebrands commonly generated by wildfires in Southern Europe were determined under laboratory conditions. All the firebrands tested showed 100% ignition frequency but with a wide range of time to ignition and flaming duration. Weight loss during combustion was exponentially related to time, and there was a decrease in the ratio of the weight at temperature T to the initial weight with increasing temperatures. In our experimental conditions, there was a significant effect of fuel moisture content on time to ignition, flaming duration, combustion and thermal decomposition. On the basis of the characteristics analysed, three firebrand groups have been identified in relation to spotting: heavy firebrands with ability to sustain flames, efficient for long-distance spotting (pine cones); light firebrands with high surface-to-volume ratio, efficient for short-distance spotting (leaves and thin barks); and light firebrands with low surface-to-volume ratio, efficient for short and, occasionally, long-distance spotting (all the other types of firebands).